1. Technical Field
This disclosure relates generally to a control apparatus for internal combustion engines.
2. Background Art
Belt transmission systems are known which work to transmit power among an internal combustion engine, an electric motor, and an accessory mounted in, for example, an automobile using a belt. Japanese Patent First Publication No. 2001-59555 teaches a belt transmission system which uses two tensioners to adjust the degree of tension of a belt to a required level. The electric motor operates selectively either in a motor mode or in a regenerative mode. In the motor mode, the electric motor works as an engine starter to rotate a drive shaft of the internal combustion engine. In the regenerative mode, the electric motor works as an electric generator which is driven by the output power of the internal combustion engine. In recent years, attention has been focused on use of the electric motor in the motor mode to assist in driving the internal combustion engine.
Most electric motors used in the above type of belt transmission systems have the property that the degree of output torque of the motor is maximized when the speed of the motor is in a low range. This may lead to a risk that when the electric motor is actuated in the motor mode to start the internal combustion engine, and the speed of the electric motor becomes high due to stretching of the belt or swinging of the tensioners before the torque, as produced by the motor, is transmitted to the drive shaft of the internal combustion engine, the electric motor fails to produce the maximum torque or that when the torque of the electric motor starts being transmitted to the drive shaft of the internal combustion engine, an output shaft of the electric motor rotates without being subjected to any resistance, so that the speed of the electric motor rises quickly, thereby resulting in a failure in producing the maximum torque.